The Gympie-Gympie (pronounced gimpey-gimpey) is one of four species of stinging tree of the family Urticaceae in Queensland, Australia. It is said to have the most painful sting of any plant, not only in Australia, but the World.
“I like it when a flower or a little tuft of grass grows through a crack in the concrete. It’s so fuckin’ heroic.” – George Carlin
Although called a tree, the Gympie-Gympie is a soft-wooded shrub that can reach 4-5m, but is often found as a smaller shrub around 0.1-1m tall. It has broad, oval or heart-shaped leaves (which appear furry due to a dense covering of tiny stinging hairs) with saw-tooth edges, and white or purple-red fruit. The stems and fruit are also covered in the stinging hairs.
When touched, the tip of the hairs break off which turn the hairs into a self-injecting hypodermic needles. It is reported that brushing against it is like being burnt with hot acid and electrocuted at the same time.
The actual chemicals contained in the toxin are not completely understood; however, it is probably a peptide (organic chemical molecules made from linking amino acids together in a certain order) called moroidin, hence the plant’s taxonomic name Dendrocnide moroides.
After a person has been stung, the small hairs can become embedded in the skin, which can lead to long-term pain and sensitivity – there are many accounts of people suffering heavily for months from a sting.
Worse still, the Gympie-Gympie is just as capable of stinging when its leaves are dead. The toxin in the hairs seems unaffected by age.
One account a soldier in the bush during World War II was caught short of toilet paper, used the wrong leaf, and was in so much pain that he shot himself in an attempt ease the pain. In 1866 a surveyor reported that his pack horse was stung by the plant, went mad and died in two hours.
“…and then, I have nature and art and poetry, and if that is not enough, what is enough?” – Vincent van Gogh
Knowledge Guild 
Stinging nettle (Uritica dioica), a short, bushy plant growing in the US, is no picnic either, I can tell you from personal experience, though I would not likely shoot myself over exposure to it.
On a more positive note, its leaves and roots appear to have a number of medicinal uses.
Interesting. Does it look dangerous? I ask merely because, rather unfortunately, the Gympie Gympie looks completely benign – plain and green.
“Does it look dangerous?” – I suppose you would have to judge that for yourself, from the picture of it that I posted below.
– I sent an instant reply which does not load images. So I had not seen that one ;)
That occurred to me – after I had posted my comment. Sorry.
I visited that area of Oz and as of late have been experiencing a burning, electric type burn especially at night upon going to sleep and the pain is so bad that I can find no comfortable location for my arms to rest and go back so sleep. As I type this message my left arm feels like a nub. My question is; Are there any long term effects of this toxin that appear later in life and if so are there any medicines to deal with the pain?
I suggest consulting a physician, urgently. If you already have, another one.